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[0001] This application claims the priority benefit of Taiwan application serial no. 90100588, filed Jan. 11, 2001.
[0002] 1. Field of Invention
[0003] The present invention relates to an optical pathway design. More particularly, the present invention relates to an optical pathway for a reflective liquid crystal projector.
[0004] 2. Description of Related Art
[0005] In recent years, the use of liquid crystal display devices have become more widely used. For example, liquid crystal displays are frequently used in televisions, handheld computers, and projectors. In general, the optical projection system inside a liquid crystal projector can be classified into an off-axial type and on-line type. Off-axial design indicates that the incoming light beam from a light source and the out-going light beam from the optical system are not on the same horizontal line. On the other hand, on-line design has both an incoming light beam and an out-going light beam on the same horizontal axis. At present, the method of projection of a projector is further divided into a front projection type and a back projection type. Most back projection types of liquid crystal projectors employ an on-line optical pathway design. In the field of liquid crystal projector design, projection quality, weight and volume of the optical system are all critical in the production of a fine projector.
[0006]
[0007]
[0008] The aforementioned conventional reflective liquid crystal projectors use an optical path design that relies on dichroic mirrors (DM) and polarizing beam splitters (PBS) to split white light into the three primary colors, red, green and blue. However, the colored light may still contain some strayed light from other colors. The contamination is outside the sphere of control of a liquid crystal panel. Ultimately, a heating problem may occur in various optical paths leading to the appearance of strayed lights that may affect contrast when the liquid crystal panel is in a dark state. Moreover, these strayed lights may lead to impure color when the liquid crystal panel is in a bright state. Furthermore, heat generation may also affect the transparency of optical components.
[0009] In addition, three polarizing beam splitters and an X-cube dichroic prism are required in the optical system shown in
[0010] Accordingly, one object of the present invention is to provide an optical pathway design for an optical system. The design utilizes a dichroic mirror and a polarizing beam splitter to serve as a beam-splitting system so that any strayed lights are reflected out of the optical system, thereby reducing heat for various optical paths.
[0011] A second object of this invention is to provide an optical pathway design for an optical system. The design utilizes a dichroic mirror and a polarizing beam splitter to serve as a beam-splitting system so that overall weight and production cost of the optical system is lowered.
[0012] To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an optical pathway design for an optical system. In the design, white light from a light source travels to a S-P converter. The light is converted into S-polarized light. The S-polarized light travels to a first color selector so that the S-polarized green light within the light beam is converted into P-polarized green light (GP). The red and the blue light remain S-polarized (RS, BS). The green light GP, the red light RS and the blue light RS travel to a polarizing beam splitter. The polarizing beam splitter permits the green light GP to pass through while reflecting the red light RS, and the blue light BS. The reflected red light RS and the blue light BS travel to a dichroic mirror so that the red light RS and the blue light BS are split apart. A plurality of absorbing filters or dichroic mirrors are installed along the optical paths of the green light GP, the red light RS and the blue light BS. Hence, strayed lights of each color are absorbed or deflected out of the optical system. Green light GS, red light RP, and blue light BP reflected back from various color liquid crystal panels are integrated together through a polarizing beam splitter. Through a second color selector, the S-polarized green light GS is converted into P-polarized green light GP. Finally, the green light GP, the red light RP, and the blue light BP pass through a projector lens before projecting onto a screen.
[0013] The invention also provides an alternative optical pathway design for an optical system. In the design, white light from a light source travels to an S-P converter. The light is converted into S-polarized light by the S-P converter. The S-polarized light then travels to a polarizing beam splitter so that the light is reflected to a dichroic mirror. The dichroic mirror permits red light RS and blue light BS to pass through while reflecting green light GS. The reflected green light GS passes through a dichroic mirror so that any strayed lights are deflected out of the optical system. The red light RS and the blue light BS travel to a dichroic mirror so that the red light RS and the blue light BS are split apart. Finally, the green light GP, the red light RP, and the blue light BP pass through the projector lens before projecting onto a screen.
[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
[0015] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
[0022] Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
[0023]
[0024] The red light RS, the blue light BS, and the green light GP travel to a polarizing beam splitter
[0025] P-polarized red light RP, S-polarized green light GS, and P-polarized blue light BP are reflected from the red liquid crystal panel
[0026]
[0027] The red light RS, the blue light BS and the green light GP travel to a polarizing beam splitter
[0028] P-polarized red light RP, S-polarized green light GS, and P-polarized blue light BP are reflected from the red liquid crystal panel
[0029]
[0030] The white light WS travels to a light polarizing beam splitter
[0031] The reflected green light GS travels to a dichroic mirror
[0032] P-polarized red light RP, green light GP, and blue light BP are reflected from the red liquid crystal panel
[0033]
[0034] The white light WS travels to a polarizing beam splitter
[0035] In the fourth embodiment, a dichroic cube
[0036] In conclusion, the advantages of this invention include:
[0037] 1. Dichroic mirrors and polarizing splitters together forms a beam-splitting system that deflects strayed lights from the optical system. Hence, heat reduction along the optical paths is improved.
[0038] 2. Using a multiple of dichroic mirrors and a polarizing beam splitter to serve as a beam splitting system, only one prism is employed. Hence, weight and production cost of the optical system is lowered.
[0039] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.